Lithography is a key process in the fabrication of semiconductor integrated circuits and many optical, magnetic and micromechanical devices, including magnetic data storage disks, CD discs and DVDs. Lithography creates a pattern on a thin film carried on a substrate so that, in subsequent process steps, the pattern can be replicated in the substrate or in another material which is added onto the substrate.
Conventional lithography typically involves applying a thin film of resist to a substrate, exposing the resist to a desired pattern of radiation, and developing the exposed film to produce a physical pattern. In this approach, resolution is limited by the wavelength of the radiation, and the equipment becomes increasingly expensive as the feature size becomes smaller.
Nanoimprint lithography, based on a fundamentally different principle offers high resolution, high throughput, low cost and the potential of large area coverage. In nanoimprint lithography, a mold with nanoscale features is pressed into a thin film, deforming the shape of the film according to the features of the mold and forming a relief pattern in the film. After the mold is removed, the thin film can be processed to remove the reduced thickness portions. This removal exposes the underlying substrate for further processing. Details of nanoimprint lithography are described in applicant's U.S. Pat. No. 5,772,905 issued Jun. 30, 1998 and entitled “Nanoimprint Lithography”. The '905 patent is incorporated herein by reference.
The usual method of pressing the mold into the thin film involves positioning the mold and the substrate on respective rigid plates of a high precision mechanical press. With such apparatus, the process can generate sub-25 nm features with a high degree of uniformity over areas on the order of 12 square inches. Larger areas of uniformity would be highly advantageous to increase throughput and for many applications such as displays.
In some applications, such as the manufacture of magnetic data storage disks CD discs and DVDs (read, write or both), it is desirable to imprint both major surfaces of an apertured substrate (top and bottom) with patterns that are in radial registration with the centers of the disks precisely aligned. The present invention is directed to apparatus which facilitates such double-sided imprinting.